While fire control systems have improved as sensor fidelity, electronic miniaturization and improvements in computational capabilities came of age, the inability to measure projectile yaw in operational weapons remains an unsolved problem that stands in the way of improvements in the precision aiming of firearms and weapons.
Specialized high-speed imaging and laboratory methodologies and equipment which are presently used to determine and measure yaw cannot be readily incorporated into firearms and weapons used in the field.
As a projectile exits a barrel it enters a “dirty” environment that obscures simple detection due to the wash of gases from the propellant (smoke, powder residue, un-burnt powder and bright illumination from the propellant burn). This situation adds to the difficulty of measuring projectile yaw and/or determining projectile motion parameters such as velocity and spin.
As a consequence, no practical or effective solution is presently available for firearms and weapons (hereinafter collectively referred to as “weapons”) to measure initial flight parameters where projectiles are fired from weapons. The measurement of initial flight parameters allows fire control systems to record repeatable bias errors which include yaw and muzzle velocity. Ballistic algorithms can use recorded measurements in lot performance to improve predictive algorithms thus improving the precision of aim points and shooting.
Numerous methods of chronographic measurement of muzzle velocity are known in the art. The rate of change of velocity (acceleration/de-acceleration) is not normally measured, however, because it must be based upon multiple measurements of projectile velocity.
Variations in projectile spin create some variation in shot-to-shot precision but the magnitude of spin variation, as compared to the effect of yaw, does not significantly affect the flight ballistics in a way that can be translated into aiming improvements. Therefore, spin has also rarely been measured, even in the laboratory.
Beyond articulating new methodologies and measurement devices that can provide improved measurement fidelity, it is useful to incorporate muzzle velocity measurement sub-systems into weapon kits to further optimize a weapon system's overall effectiveness. In this regard, it is instructive to first discuss some recent history regarding the use of muzzle velocity measurement and air-burst programming technology fitted to military platforms.
Measuring muzzle velocity: First, one should recognize that radar has been used to measure projectiles in flight since the Second World War. Today, the US Army has incorporated Doppler muzzle velocity radars as standard equipment fitted to the Army's new 155 mm US Army Paladin and 155 mm M777A1. The artillery fire control computers then use regressive algorithms in the ballistic computers to progressively adjust and refine the firing solutions. While radars and advanced fire control algorithms are “standard stuff” in modern artillery systems, the cost of Doppler radars and the threat posed by anti-radiation missiles precludes wider use of radar on smaller ground platforms. While radar costs may reach a cost point where the devices can be incorporated into smaller weaponry, it is possible to use alternative measurement methodologies and modify the time of burst or actual muzzle velocity for improved terminal effect.
Measuring muzzle velocity and programming ammunition: In the 1990s, Oerlikon invented the “AHEAD” technique of programming ammunition by measuring the velocity of an ammunition projectile passing through a muzzle break and then modulating an electro-magnetic signal to program ammunition passing through a muzzle break with a burst time optimized for the actual measured muzzle velocity for that projectile. This technique was disclosed in U.S. Pat. No. 5,814,756. The resulting product revolutionized gun based air-defense guns and is incorporated into the Rheinmetall Skyguard Air Defense system. There are two drawbacks of the AHEAD system: (1) the energy requirements (amperage) required to program a shot make it difficult to transition this technology to dismounted ground infantry systems and (2) the muzzle break is bulky with large conductive rings. The AHEAD technology has proven successful in the air defense system, however, and the technology has been successfully incorporated into the BAE Hagulunds CV 9035 system used by Denmark and the Netherlands.
Fire control, remote weapon stations and remote turrets: During the 1980s and 1990s armored vehicles and tanks acquired sophisticated fire control systems. Militaries worldwide have made increasing use of overhead weapon stations and remote turrets. In the United States, the initial fielding of the Kongsberg M151 Remote
Weapon Stations took place on the US Striker vehicle program. Later, the same Remote Weapon System was adopted as the Common Remote Weapon Stations (CROWS) that was fielded throughout the US military inventory. The fire control systems, built and fielded in this period were designed to range targets, calculate vertical and horizontal aim adjustments based on firing tables and atmospheric sensors where the fire control solutions and algorithms were based on calculations that relied on the mean ammunition muzzle velocities of ammunition lots retained in a very large reserve ammunition stock. As stocks age, muzzle velocities change and eventually ammunition increasing muzzle velocity variations necessitates that the Army destroy stocks of ammunition.
In-bore ammunition programming: In the first decade of the 21st century NAMMO's MK285 cartridge introduced the first airburst programmable 40 mm cartridge that was exclusively fired from the MK47 system, The MK47 was a package with an improved video based fire control and a weapon with a breach to accommodate “in bore” galvanic programming as taught in the Larson U.S. Pat. Nos. 6,138,547 and 6,170,377. This system was acquired and fielded in SOCOM. During this period, other “in bore” techniques were also patented and developed by IMI, Rheinmetall and Picatinny Arsenal. The technical reasons that “in bore programming” techniques were initially favored was that the “in bore” approach provided bi-directional interfaces and certain electronic limitations in the 1990s influenced the system designers of that period to favor galvanic connections that accommodated (a) relatively high amperage levels, (b) capacitors with limited storage and (c) reserve batteries designs with slow power rise times. Yet, while there were benefits to “in bore programming” in the 1990s, one significant issue created a barrier to wide adoption of the technology: The cost associated with modifying firing platforms and fire controls proved to be significant and ultimately resulted in an insurmountable barrier to wide adoption of in-bore air-burst ammunition. During the recent war in Afghanistan, the USMC modified a limited number of their M1A1 tanks and fielded Rheinmetall's DM11 for restricted use in combat operations. The USMC's experience with the DM11 is instructive as the expense of modifying the USMC's M1A1 tank fleet to accommodate in-bore programming has stalled the project as the cost of upgrading all the USMC's M1A1 tank fleet proved unaffordable in a budget restricted environment.
Post-shot programming kit for programmable airburst ammunition: Again, one should recognize the AHEAD system was the first “post-shot programming” device fielded but, as noted previously, power demands and the cumbersome mass of the muzzle device precluded use of the system in dismounted weapons. As the defense industry entered a new millennium of the 21st century, Moore's law continued to drive advancements and the electronic components advancements made “post-shot programmable ammunition” practical and affordable with the added benefit of being simpler to integrate into weapon platforms. In the second decade of the 21st century, wireless RF and optical devices became ubiquitous in homes and businesses so the apprehension regarding wireless solutions faded. With wireless RF and optical solutions, system integration costs fell and the cost associated with upgrading systems to incorporate air-burst technology have fallen. Recognizing this, NAMMO and Singapore introduced “post-shot” RF programming and Rheinmetall introduced their DM131 which is an optical (IR) based programming as described in their U.S. Pat. No. 8,499,693.
Z-range velocity measurement and post-shot airburst programming kit: In configurations where programmable “airburst” ammunition is fired and where “post-shot programming” is used, the programming of a uniquely optimized time-of-flight for a fired projectile can provide military forces with distinct operational advantages. The introduction of “post-shot programming” kit that includes a muzzle velocity measurement device, ballistic calculator and programmer (or transmitter) affords military customers the ability to construct a system where the individual muzzle velocity of each shot is measured and a ballistic calculator computes an optimized flight time that is then transmitted to a projectile. By utilizing such a kit, military personnel can minimize the “range error” associated with muzzle velocity variation, improve precision, improve terminal effects and reduce ammunition expenditures in defeating targets. To illustrate the value of such a kit one can use a 40 mm×53 High velocity grenade as an example. Generally, a 40 m×53 grenade lot will exhibit 5-10 meter per second muzzle velocity variation within a sample. A 40 mm grenade fired at a range corresponding to 1500 meters would have 9.5 seconds of flight time. With a mean muzzle velocity variation of +/−5 meters per second multiplied by the grenade's 9.5 seconds of flight time, a volley of ammunition will generally fall at range distance 90 meters apart. At this range, the projectile is traveling at a velocity of 1 meter per millisecond and the electronic circuitry of the air-burst munitions' timing circuitry is within a few milliseconds of precision. In providing a device that (1) measures the actual muzzle velocity, (2) given a range, calculates “z” ballistic range error in a ballistic calculator and a corresponding optimized time-of-flight, and (3) programs the ammunition “post-shot” to detonate a prescribed flight duration in a weapon kit, allows the military to upgrade weapons so that weaponry will accurately air-burst at a programmed range.
Z-range muzzle velocity measurement and regulation kit: Current propellant and mechanical technology limits the repeatability of ammunition muzzle velocity which varies in both lot-to-lot and shot-to-shot conditions. Environmental parameters further complicate the repeatability of muzzle velocity as it is well known that the temperature of ammunition propellant influences a projectile's muzzle velocity. At distance, projectiles with a higher muzzle velocity travel farther and hit vertical targets at a higher elevation when compared to slower traveling projectiles. Muzzle velocity effects both the range “z” error and the vertical target impact “y” error. Like range “z” error programming, it is possible to use a projectile's actual measured muzzle velocity and, with a kit, consistently reduce or increase the muzzle velocity of projectiles to a standardized slower velocity and improve the shot-to-shot performance of a weapon system. In significantly reducing or increasing the variation in muzzle velocity to a target velocity, a weapon system's precision can be increased. Some ammunition families use projectiles that are metallic and are subject to the influence of magnetic forces. Solenoids are well known to create mechanical force actuators whereby electric current applied to a coil creates a magnetic force which, in turn, creates a mechanical force. A kit composed of a device that (1) measures the actual muzzle velocity in the barrel or in a flash suppressor, (2) given a known magnetic characteristic of a bullet design or model, calculates a unique force to apply to each specific projectile transiting from a muzzle into a flash suppressor or muzzle break and (3), where the force applied after measurement, reduces the velocity to a standardized and repeatable velocity for a given type of ammunition. A kit adapted or incorporated into a weapon, configured accordingly, could deliver ammunition traveling at a highly repeatable muzzle velocities and reduce shot-to-shot dispersion thus improving the precision of the entire weapon system.
New kits measuring muzzle velocity, precisely programming unique air-burst duration or kits adjusting muzzle velocity to a reputable target velocity are relevant as currently available fire control platforms are only optimized for x and y (lateral and vertical) error correction and are not configured to correct muzzle velocity and program z (range) error. As discussed herein the modification of existing fire-control sub-systems with new algorithms, new electronics and sensors can prove to be complex and costly. Accordingly, kits that modify existing fire controls should be considered.
In many projectiles, the variation in muzzle velocity is a significant factor contributing to dispersion of impact points and overall system error. Accordingly, a system that measures muzzle velocity coupled with a system that adjust air-burst programming of air airburst ammunition will improve the terminal effects of air burst ammunition. Moreover, a device that measures muzzle velocity coupled with a system that influences the muzzle city of an exiting projectiles can reduce the dispersion of impacting projectiles.